You have to rely on your decades-long confirmation bias.
I doubt the author (or anyone) goes back to their interview notes a year after hiring the candidate to see how much they got right.
I doubt the author (or anyone) goes back to their interview notes a year after hiring the candidate to see how much they got right.
If you hired only one guy, who's to say that the others you rejected would have performed better or worse?
If you hired 3 for similar positions, you can start making guesses from interview performances and (in)validating them one year after. But as you said I don't think it's done in practice anyway.